Calculate IPv4 CIDR subnets (/0 to /32). Computes network address, broadcast address, first and last usable host IPs, wildcard mask, and binary subnet masks.
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The IP Subnet Calculator performs IPv4 subnetting calculations based on Classless Inter-Domain Routing (CIDR). It calculates the network ID, broadcast address, usable host IP range, wildcard mask, and total usable host capacity for network engineers and system administrators.
N_{\text{hosts}} = 2^{32 - \text{prefix}} - 2, \quad \text{Network} = \text{IP} \ \& \ \text{Mask}, \quad \text{Broadcast} = \text{Network} \ | \ \sim\text{Mask}In standard subnets (prefix ≤ 30), two addresses are reserved: all 0s for the network ID and all 1s for the broadcast address.
Scenario: Subnetting 192.168.1.100 with a /24 CIDR prefix (255.255.255.0)
CIDR prefix: /24 (32 - 24 = 8 host bits).
Total IP addresses: 2⁸ = 256.
Usable hosts: 256 - 2 = 254 hosts.
Network address: 192.168.1.0; Broadcast: 192.168.1.255.
Usable host range: 192.168.1.1 through 192.168.1.254.
Classless Inter-Domain Routing (CIDR) represents an IP address and its associated subnet mask using a slash followed by the count of leading 1s in the mask (e.g., /24 means 24 mask bits or 255.255.255.0).
The first address (where all host bits are 0) identifies the network itself. The last address (where all host bits are 1) is reserved as the local broadcast address.
Private IP addresses reserved for home and enterprise local networks: Class A: 10.0.0.0/8; Class B: 172.16.0.0/12; Class C: 192.168.0.0/16.
Under RFC 3021, /31 subnets (with only 2 addresses total) are used for point-to-point router links without reserving network or broadcast addresses, conserving IPv4 space.
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